this is a library catalog/library inventory, undertaken by the head librarian of the Conservatory Library, Alfred Wotquenne (better known for his musicology and editorial work, for the "W." attached to works by C.P.E. Bach and C. Gluck that originated with his thematic catalogs of their works back in 1904 - which Internet Archive also has, and which were used for 75 years or so in the former case. These aren't opera libretti, I don't think, but rather lists of what the conservatory libraries do and don't have...

Saving rating until I've had a better look at the scan itself, but until I've worked out how to change tags m'own'self (if there is such a thing as... maybe someone told me; I forget, sorry)- I thought I'd put a note here. Sorry!

- E.S.